The present invention relates generally to monochrome and color printing systems, and more specifically, to image calibration of such printing systems.
In printers, especially high quality monochrome and color printers, multiple imaging systems need to unite to form a single image. Typically, these multiple systems are not co-located and attempts are constantly being made to make certain that these systems align. The process of calibrating multiple systems to guarantee alignment is frequently referred to as Color Plane Registration (CPR).
If different colors planes (e.g., cyan (C), magenta (M), and yellow (Y)) are not exactly aligned, then the quality of an image will suffer. There are many very accurate CPR processes, roller aligners, belt procedures, et cetera, to ensure very precise alignment and registration of multiple systems. Yet, despite very precise CPR procedures developed, many manufactures, especially of color laser printers, struggle to manufacture printers that produce very high quality images at reasonable costs.
With constant pressure to reduce manufacturing costs, massively reproduced parts are often manufactured with variances in shape and consistency and affect the ultimate quality of images. Additionally, environmental factors, such as temperature fluctuations, humidity variances, can also cause printing systems to have trouble achieving accurate CPR.
Laser printers, for instance, typically use some type of photoconductor drum and rollers. Instructions from the printer""s processor rapidly turn on and off a beam of light from a laser. This beam is deflected across the imaging drum or belt by means of a mirror. Where light hits the negatively charged film on the surface of the drum, the charge is changed to match that of the paper, which is charged positively as it enters the printer. As the drum begins to rotate, a series of gears and rollers draws in a sheet of paper. As the drum turns, it comes into contact with the toner cartridge. The negatively charged toner particles are attracted to the drum areas exposed to the laser. As the sheet of paper moves through, it is pressed against the drum and its electrical charge pulls off the toner. This process is repeated for the other colors, and then fusing rollers bind the toner to the page. If the imaging drums and rollers contain imperfections, then CPR cannot be fully achieved and image quality suffers.
A calibration system and method for printers is described. The system and method ensures that images are properly aligned in printing systems that use one or more non-ideally shaped image transfer elements and/or when the one or more image transfer elements move eccentrically. In a described method implementation, a non-circular or eccentric imperfection associated with an image transfer element is determined. The image transfer element is then moved at a non-constant angular velocity to compensate for the non-circular imperfection.